Duane wasn't trying to show off or override the composition, he added what was tasteful and improved the overall cohesiveness of the song.
Not many guitarist can play with taste, those that do are who I consider great. I'm never blown away by someone that can just shred, it does nothing for me. When they can phrase their playing it's just like singing with the guitar, and Duane is one of the greatest of all time because of this. Anyone can learn guitar and scales, but you can't teach phrasing, feeling and creativity.